The correlation between composition and structure of unpoled relaxor ferroelectric (1-x)Pb(Zn1/3Nb2/3) O-3-xPbTiO(3) (PZN-PT) solid solutions around the morphotropic phase boundary was studied by Rietveld refinement of X-ray powder diffraction patterns of crystals with x = 0.06-0.13 grown by a solution technique. It was found that PZN-PT exists with the rhombohedral structure only below x = 0.06. The rhombohedral R3 in phase coexists with the tetragonal P4 min phase between x = 0.08 and 0. 11 and above x = 0. 11 PZN-PT is purely tetragonal. In addition a metastable monoclinic phase (Pm) forms during cooling after crystal growth in the composition range x = 0.06-0.11. The volume fraction of this monoclinic phase is a maximum in the most interesting composition range, i.e. x = 0.08-0.09. The amount of monoclinic phase is enhanced further by mechanical treatment as the pulverization of the crystals for X-ray powder diffraction analysis which induces a tetragonal-to-monoclinic phase transition. (C) 2003 Elsevier Science B.V. All rights reserved.